Verizon and AT&T abandoned offering new customers a way to get an unlimited data plan some time ago. Sprint still has such a plan in place, and more recently T-Mobile announced it now has a way for its customers to get a truly unlimited data plan, with no caps or data throttling.

Now it's US Cellular's turn to tempt people with an ultimate data plan, but there is a small catch involved. The company's Facebook page announced today that the fifth largest wireless carrier is now offering a $40 per month plan that offers true unlimited data for its 4G LTE smartphones. News.com adds that for an additional $20 a month, you can add tethering to that unlimited plan.

Sounds good, doesn't it? It is, but the catch is that this offer is not going to last forever. US Cellular says it will end on January 31st, 2013.

So, at least for the next two months or so, the third, fourth and fifth biggest wireless carriers all offer truly unlimited data for smartphones, while Verizon and AT&T are trying to push their recently launched shared data plans to new customers. It will be interesting to see which plans are more popular with the general public.